Vibration generator



5, 1958 P. ZERIGIAN 2,846,598

VIBRATION GENERATOR Filed Jan. 13, 1956 4 Sheets-Sheet 1' FIG. I.

68 72 74 N V EN TOR I PETER ZER/G/A/V Aug.5,1958 "RZ'ERIGIAN 2,846,598

VIBRATION GENERATOR Filgd Jan. 13, 1956 4 Sheets-Sheet 2 FIG. 5.

INVENTOR PETER ZER/G/AN ATTORNEY P. ZERIGIAN VIBRATION GENERATOR Aug. 5,1958 4 Sheets-Sheet 3 Filad Jan. 13. 1956 FIG. 8'.

V NT PETER 25%651/1 A TTOIPNEY g- 5, 1953 P. ZERIGIAN 2,846,598

VIBRATION GENERATOR Filed Jan. 13. 1956 4 Sheets-Sheet 4 I ["{jlNlTEFLExuryu. TIFFNESS I WITHENDS FULLYIRESTRAINED FINITE FLEXURAL STIFFNESSWITH ZERO Em) RESTRAlNT l STRING FIXED ENDS ZERO FLEXURAL STIFFNESS 1/FIG. /2.

- DEFLECTION IN VEN TOR PETE)? ZE/P/G/AN yaw e z/%@ ATTORNEY VIBRATIONGENERATOR Peter Zerlg ian, Bedford, Mass., assignor, by mesneassignments, to The Calidyne Company, Inc., incorporation ofMassachusetts Application January 13, 1956, Serial No. 558,922

14 Claims. (Cl. 310-27) This invention relates to vibration testequipment and more particularly to the suspension or flexures forsupporting the moving element thereof.

Heretofore it has been the practice to support the moving element orarmature by means of cantilever flexures which are rigidly secured atone end to the sup porting base and pivotally attached at the other endto the armature to permit substantially axial movement United StatesPatent thereof while restraining the lateral movement of the armature.Flexures of this type, which are described in United States LettersPatent No. 2,599,036 to Efromson and Lewis, have been widely used andproved generally satisfactory. However, as this type of test equipmenthas increased in size, several inherent disadvantages of the cantilevertype flexures have been more apparent. First, with cantilever flexurestrue linear movement is only approximated so that the axial movement ofthe armature is limited, and second, with increasing weight of thearmature and connected load, the design of a satisfactory cantilevertype flexure becomes increasingly difficult if not impossible.

It is therefore the principal objects of the present invention toprovide a support for the armature of vibration test equipment whichpermits true linear movement of the armature in an axial direction,which restrains the armature from deflection in a lateral direction,which can support large loads, and which'advances the art generally.

According to the present invention the means for supporting the armaturestructure with freedom of movement in an axial direction whilerestraining the armature structure in a lateral or radial directionrelative to an associated supporting core structure comprises a pair offlexures in spaced axial relation and preferably attaching to theopposite ends of the armature structure. Each of the flexures comprisesat least one strap or leaf of a resilient material such as a suitablemetal or laminated plastic resin which is interposed between thearmature and core structure, there being a respective connection betweeneach end of the strap and the adjacent structure. One or more of theconnections associated with each strap, preferably those adjoining thecore structure, are provided with a resilient element of an elastomersuch as natural or synthetic rubber or'other material having similarelastic and resilient properties. The elastomer elements are preferablyin the form of plates or blocks abutting the opposite faces of the strapso that the elements are stressed in shear by the movement of thearmature, thereby both to provide for a small movement or relief in adirection lengthwise of the strap and simultaneously permitting turningor rocking of the strap and thus materially increasing the permissibledeflection of the strap.

These and other objects and aspects of the invention will be apparentfrom the following description of several specific embodiments of ourinvention which refers to drawings wherein:

Fig. l is a plan view of an electrodynamic vibration test machinewherein is used a first embodiment of the invention;

Fig. 2 is a sectional view on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary enlarged sectional view taken on line 3-3 ofFig. 1;

Fig. 4 is a plan view of another type of electrodynamic vibration testmachine wherein is used a second embodiment of the invention;

Fig. 5 is a sectional view on line 5--5 of Fig. 4;

Fig. 6 is a fragmentary elevation showing the details of the ilexureconnection used in the embodiment of Figs. 4 and 5;

Fig. 7 is a plan view of an electrodynamic vibration test machinegenerally similar to that shown in Figs. 4 and 5 but using a thirdembodiment of the invention;

Fig. 8 is a sectional view on line 88 of Fig. 7;

Fig. 9 is a plan view of a modified ilexure connection for use with thevibration test machine shown in Figs. 7 and 8;

Fig. 10 is a side elevation view in partial section of the fiexure ofFig. 9;

Fig. 11 is a schematic view showing the deflected configuration of oneof the flexures shown in Figs. 1 and 2; and

Fig. 12 is a graphic view of the load as a function of the deflectionof. one of the flexures of Figs. 1 and 2.

The electrodynamic vibrating testing machine or shaker shown in Figs. 1and 2 comprises a core structure of a low magnetic reluctance materialsuch as soft iron which includes a central cylindrical pole piece 20concentrically arranged with respect to an outer cylindrical shellmember 22 of a material having analogous magnetic characteristics. Adirect current field winding 24 is positioned by means of non-conductingspacers 26 within the cavity between the shell 22 and the pole piece 20.The ends of the winding cavity are enclosed by cover plates such asdiscs 28 and 30 also of low reluctance material which are attached tothe outer shell 22 by bolts 32. Each of the end discs 28 and 30 areprovided with central apertures through which the pole piece 20projects, the diameter of the aperture in the upper disc 28 beingsubstantially the same as that of the outer diameter of the pole pieceso that there is a minimum of clearance therebetween and the magneticreluctance of the joint is minimized. The aperture in the other disc 30is of greater diameter so that a cylindrical air gap is formed betweenthe wall thereof and the outer surface of the pole piece 20. A strongunidirectional flux is established in the magnetic circuit of the corestructure consisting of the central pole piece 20, the upper disc 28,the outer shell 22, the lower disc 30 and the cylindrical air gap by theflow of a direct current through the field winding 24. On the face ofthe wall of the aperture of the disc 30 defining the air gap is awinding 34, the turns of which are short-circuited to dampen theresonant movements of the armature structure 36 as described in detailin the copending application Serial No. 517,543 of Robert C. Lewis,filed June 23, 1955.

To prevent stray leakage flux in the vicinity of the top of the shakeran auxiliary winding 38 is supported between the end disc 28 and acircular plate 40 of a low reluctance material by spacers 42. Thecircular plate 40 is secured to the top of the central pole piece 20 bybolts 44, and the outer peripheries of the disc 28 and plate 40 arebridged by a: non-magnetic strap 46, whose ends are secured by screws48. The amount and direction of flow of direct current through theauxiliary winding 38 are made such as to produce a flux in theprojecting end of central pole piece 20 and plate 40 substantially equalto and opposite in direction to the fiux produced in these corestructure elements by the field winding 24 so that the leakage flux inthe vicinity is substantially zero.

The armature structure 36 comprises four elongated struts 50 whose upperends are secured respectively by screws 52 in slots in the ends ofintegrally formed transverse members 54 which are normally disposed toeach other. In the upper surfaces of the transverse members 54 areprovided threaded recesses 56 for connecting or attaching a test load(not shown). The struts 50 extend through apertures in the end disc 28and corresponding aligned longitudinal slots in the plate and theperiphery of the central pole piece 20 so that the lower ends of thestruts can be secured in bottom transverse members 58 in an analogousmanner to that in which the upper ends are secured as described above.An armature coil 60 is bonded, for example, by an adhesive resin, to thestruts below bosses 62 projecting outwardly from the edges thereof sothat the coil is supported in the armature gap of the core structure.

The impressing of an alternating current upon the armature coil producesan alternating flux which interacts with the above mentioned direct fluxacross the air gap resulting from the flow of a direct current throughthe field winding 24 whereby the armature structure 36 movesreciprocally with respect to the core structure at a frequencycorresponding to the frequency of the alternating current in thearmature coil as is well known to those skilled in the art. It is ofcourse necessary mechanically to guide and support the armaturestructure 36 during its reciprocal movement to limit its axial traveland to prevent rubbing contact with the core structure.

It is to such guiding and supporting means for the armature structure 36that my invention is particularly directed. To this end a pair offlexures 66 are provided, the spacing of the fiexures being such thatthey are located respectively at the opposite ends of the armaturestructure 36. Each fiexure 66 includes a leaf spring or a strap 68 of aresilient material, for example, a suitable bronze, tempered steel orlaminated phenolic plastic resin, which is attached at its midpoint tothe armature structure 36 and at its opposite ends to the core structureby means of connections described in detail below. The midpointconnection is rigid, i. e., there is substantially no relative movementbetween the strap 68 and the adjacent elements of the armature structure36. To this end, each of the fiexure straps 68 is clamped respectivelybetween a square boss 70 disposed beneath the transverse armaturemembers 54 (or 58) "and an associated plate 72 of the sameconfiguration. This clamping relationship is maintained in each instanceby four cap screws 74 which project through aligned apertures in theplate 72, the strap 68 and boss 72 to engage threaded recesses in thetransverse members 54 (or 58).

It will be evident that with 'both ends of the straps 68 attached to thecore structure, deflection of the flexures 66 is impossible unless someflexibility or resiliency is introduced to give relief in a directionlengthwise of the straps. Such resiliency is provided by flexibleconnections 75 interposed between the ends of each strap 68 and the corestructure, the details of which are shown in Fig. 3. Each connection 75includes two backing members such as the clamping plates 76 and 77 whichare disposed adjacent the opposite faces of the corresponding end of thestrap 68. interposed between each of the backing plates 76 and 77 andthe corresponding strap face is an element such as the block 78 of anelastomer material for example natural or synthetic rubber. Theelastomer blocks 78 are compressed between the backing plates 76 and 77by two cap screws 80 each of which projects through aligned apertures inthe top backing plate 76 and a metallic bushing 82, to engage a threadedrecess in the bottom backing plate 77. It is to be noted that theaperture through the strap for accommodating the bushing 82 ismaterially greater in diameter than the bushing so that there 18normally no contact between the bushing and the strap, the restrainingof the strap in a direction longitudinal thereof being due entirely tothe shear in the blocks 78. The connections 75 are secured to the corestructure by cap screws 84 (Figs. 1 and 2) which pass through the endsof the lower backing plates 77 to engage the ends of the core structure.

In Fig. 11 one of the fiexures 66 is shown schematically, the solidlines indicating its configuration in an unstressed position as when thearmature structure 36 is positioned normally so that the armature coil60 is disposed centrally of the air gap. The broken lines indicate in agreatly exaggerated scale, the configuration of one of the flexures 66when the armature structure 36 is displaced downwardly, axially from itsnormal position. It is to be noted that the boss 70 and the associatedplate 72 prevent the bending of the portion of the strap 68 adjacenteither side its midpoint which is clamped therebetween so that theportions of the strap between the end connections 75 and the boss can beconsidered as separate beams whose illustrated deflection is madepossible by the yielding inherent in such end connections, a combinedrocking and pullout of the end of each strap 68 relative to the corestructure taking place as the fiexures 66 are deflected.

In Fig. 12 is diagrammatically shown by means of a solid line, theloading as a function of deflection of a rigidly fixed end cantileverbeam such as is generally used as a fiexure for supporting shakerarmatures. It is to be noted that the load-deflection relationship issubstantially linear which is desirable. The arcuate motion due topivoting of such a fiexure is undesirable at high deflections, becauseof the introduction of second harmonic lateral motions and because ofthe greater gap clearances required due to this motion. The broken lineof Fig. 12 shows the load-deflection relationship of a member supportedas in Fig. 11 having zero fiexural stiffness, high axial stifiness, andfixed ends. In this case deflection is allowed only through stretchingin length. Such a member is represented by a wire, and is undesirabledue to its non-linearity, zero stiflness at zero deflection, and zerolateral stiffness. The dashed line in Fig. 12 shows the load-deflectionrelationship of a fiexure similar to 66 but with fixed ends. This curvehas an initial stiffness equal to that of the cantilever, so that thesolid and dashed lines have the same slope at small deflections. Thestiffness of the fixed end member rises rapidly wtih deflection, as doesthat of the wire. The introduction of end flexibility throughconnections 75 and proper proportioning of the straps 68 allows a closeapproximation to the liner deflection of the cantilever as shown by thesolid line.

I have also found that to obtain the above discussed desirablechracteristics in a supporting fiexure it is not necessary for the strap68 to be continuous so long as tharmature structure ends of thedeflecting portions thereof are interconnected by some type of rigidlink. One example of such a fiexure is shown in the shaker illustratedin Figs. 4 and 5. The core structure of this shaker comprises a hollowcylindrical shell 88 preferably cast of a low magnetic reluctancematerial, such as soft iron, having an integral central pole piece 90 sothat a cavity is formed to receive a direct current field winding 92.The winding 92 rests upon several spacer blocks 94 of an insulatingmaterial and is held in place by several spacer blocks 96 whose lowerend 98 which is in contact with the winding is also of an insulatingmaterial. The upper end of the spacer blocks 96 abut the bottom side ofan annular cover 100 which encloses the top of the winding cavity. Thecover 100 is provided with a rolled over flange 102 which iscounterbored and apertured to receive six bolts 104 securing the coverto the casting shell 88. The magnetic circuit of the core structure iscompleted by a cap 106 which is attached to the end of the central polepiece by means of bolts 108. About the periphery of the upper end of thecap 106 is provided .5 an integral annular lip 109 which forms one faceof the air gap is the magnetic circuit of the corestructure. The otherface of the air gap is formed by the wall of a circular central aperturein the cover 100. Inserted in the central aperture abutting the wallthereof is an electrically conducting cylinder 101 which acts as asingle short circuited turn to provide electrical damping of thearmature in a manner analogous to the action of the winding 34 (Fig. 2)as was discussed above.

The cap 106 is provided with a central axial recess outwardly wherefromradially extend eight equally spaced slots so that the upper end andcentral portion of the cap are divided into eight upwardly projectingfinger-like sectors. This distinctive shape of the cap 106 permits thecap to receive in its slots the corresponding arms of an armature spider110 east of aluminum or other light weight non-magnetic material. Thearmature structure is completed by an armature coil 112 which encirclesthe lower half of the spider 110 and is bonded to an annular flange 114formed integrally with the outer cylindrical surface of the spider andthe projecting arms of armature spider 110. A metallic ring 116 islikewise bonded to armature 110 and coil 112 in order to attach ilexuresas later described. A number of threaded recesses such as 118 areprovided in the top surface of the arms of the spider 110 so that a loador device (not shown) to be tested can be attached or connected to thearmature structure. Bumpers 120 of a resilient material are interposedbetween the floor of the radial slots in the cap 106 and the bottom ofthe spider 110 to limit the downward travel of the armature structure.

In a manner similar to that described above in connection with theembodiment of Figs. 1 and 2, a reciprocating movement is imparted to thearmature when the field winding 92 and the armature coil 112 areenergized by direct and alternating currents respectively. During suchmovement the armature structure is guided by four equally spaced pairsof fiexures each pair consisting of an upper fiexure 122 and a lowerfiexure 124. The upper flexures 122 are all similar in construction eachcomprising a resilient leaf spring or strap 126 Whose innermost end isrigidly connected to the annular armature spider flange 114 by a spacer127 held by two cap screws 128. The opposite end of each strap 12.6 isclamped between two elastomer blocks 130 which are compressed in arecess in the top of an H-block 132 by a backing member 134 secured byscrews 135.

The bottom flexures 124 are all also similar each comprising a resilientstrap 136 whose innermost end isattached to the bottom of the armaturering member 116 by a spacer 137 held by cap screws 138. The opposite endof each lower strap 136 is clamped between two elastomer blocks 140which are compressed between a recess in the bottom of the H-block 132and cover 100 by cap screws 135.

It will be evident that the above described fiexures 122 and 124 arefunctionally the equivalent of the flexures 66 of-the first embodimentdescribed heretofore each of the opposed straps 126 (or 136) deformingupon the axial movement of the armature structure in the same manner asthe portions of the strap 68 between the boss 70 and the connections 75as illustrated by the broken line in Fig. 11. The elastomer blocks 130(and 140) function in an analogous manner to the blocks 78 of theconnection 75 so that it is possible by proper balancing of thecantilever properties of the straps 126 and 136 and the snubbingproperties of their end flexible connections to approximate a linearload-deflection characteristic such as is shown by the solid line ofFig. 12 and discussed in detail above.

A third embodiment of the invention wherein the longitudinal axis of thefiexures does not coincide with the central axis of the armaturestructure is illustrated in Figs. 7 and 8. The core structure, otherthan the cap for the central pole piece, of the shaker shown in Figs.

8 and 9 is essentially the same as the core structure of the secondembodiment of Figs. 4 and 5 so that the elements thereof will be givencorresponding identifying numerals and need not be described further.The pole piece cap (Fig. 8) differs from the cap 106 (Figs. 4 and 5)only in that it is provided with four rather than eight radial slotsthereby to accommodate the four arms of a modified armature spider 152.The armature coil 154 is slipped on over the spider arms, and is bondedagainst a flange 156 and clamped by means of four equally spaced blocks158. Each of the blocks 158 also forms part of one of four rigidconnections attaching respectively to the armature spider 152 four upperfiexure straps 160 and 162, the midpoints of the straps resting upon thetops of the associated blocks. The straps 160 and 162 are rigidlyclamped against the blocks 158 by four plate members 164 which arebrought into forceable contact with the opposite faces of the straps bythe action of through bolts 166. The corresponding lower fiexure straps168 and 170 are similarly interposed between blocks 172 bearing againstthe bottom of the spider flange 156 and associated plate members 174which are provided with threaded apertures for receiving the threadedshanks of the through bolts 1 66.

The ends of the fiexure straps 160 and 162 are attached to the corestructure cover 100 by means of connections 175. As can best be seen inFig. 8, each end of each of the straps 160 is interposed between twoelastomer blocks 176. A spacer 178 separates the lower block from asimilar pair of elastomer blocks 180 between which is interposed theassociated end of one of the straps 162. The stacked blocks 176 and 180and the spacer 178 are held in a recess in a stand-off piece 182 by aclamping plate 184 which is secured by three bolts 186. The bolts 186pass through apertures in the stand-off piece 182 to engage threadedrecesses in the top of the core structure cover 100. The ends of thelower fiexure straps 168 and 170 are clamped in connections 188 attachedto the bottom of the cover 100. As the connections 188 are similar inconstruction to the connections 175 described heretofore, the details ofconnections 188 will not be set forth again.

In Figs. 9 and 10 are shown the details of an alternative flexibleconnection for securing the ends of upper fiexure straps 160and 162 orlower fiexure straps 168 and 170 wherein only two elastomer blocks 190are required. This is accomplished by mitering the ends of the straps160 and 1.62 to permit both straps to lie in the same plane betweenthe-blocks 190. The blocks 190 are compressed against the strap faces bybacking plates 192 held by the bolts 186 Whose threaded shanks engagerecesses in the core structure cover 100 as described above.

It will be recognized that in the third embodiment discussed above thearmature blocks 158 (Fig. 8) and the corresponding plate members 164divide the associated fiexure straps 160 and 162 into two portionswhich, as the armature structure is moved, take a similar configurationto that of the portions of the fiexure strap 68 on either side of theboss 72 as are illustrated in Fig. 11 and tie scribed above. It is,therefore, possible to balance the cantilever action of the straps andthe snubbing action of the connections 175 so that a substantiallylinear deflection relationship is obtained over a large range of loadsin a manner analogous to that illustrated in Fig. 12 and discussed indetail heretofore.

It should be understood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

What is claimed is:

1. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction whilerestraining thestructure in a radial direction relative to an associated corestructure, a pair of flexure means disposed in spaced axialrelationship, each of the fiexure means including at least onedeformable strap of a resilient material having a face whose width ismaterially greater than the strap thickness interposed between thestructures with the face of the strap disposed in the direction of axialmovement of the armature structure so that the strap is deflected by themovement thereof, and connections between each strap and the adjacentstructures for attaching the strap thereto, one of the connectionsassociated with each strap including elastomer elements which arestressed in shear by movement of the armature structure to providerelief in a direction lengthwise of the associated strap therebymaterially to increase the permissible deflection thereof.

2. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, a pair of fiexure means disposed in spaced axialrelationship, each of the flexure means including at least onedeformable strap of a resilient material having a face whose width ismaterially greater than the strap thickness interposed between thestructures with the face of the strap disposed in the direction of axialmovement of the armature structure so that the strap is deflected by themovement thereof, and connections between each strap and the adjacentstructures for attaching the strap thereto, each connection between thecore structure and a respective strap including elastomer elements whichare stressed in shear by movement of the armature structure to providerelief in a direction lengthwise of the associated strap therebymaterially to increase the permissible deflection thereof. 7

3. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction While restraining thestructure in a radial direc tion relative to an associated corestructure, a pair of fiexure means disposed in spaced axialrelationship, each 'of the fiexure means including at least onedeformable strap of a resilient material having a face whose width ismaterially greater than the strap thickness interposed between thestructures with the face of the strap disposed in the direction of axialmovement of the armature structure so that the strap is deflected by themovement thereof, and connections between each strap and the adjacentstructures for attaching the strap thereto, one of the connectionsassociated with each strap including elastomer elements abuttingopposite faces of the end of the strap so that the elements are stressedin shear by movement of the armature structure to provide relief in adirection lengthwise of the associated strap thereby materially toincrease the permissible deflection thereof.

4. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, a pair of fiexure means disposed in spaced axialrelationship, each of the fiexure means including at least onedeformable strap of a resilient material having a face whose width ismaterially greater than the strap thickness interposed between thestructures with the face of the strap disposed in the direction of axialmovement of the armature structure so that the strap is deflected by themovement thereof, and connections between each strap and the adjacentstructures for attaching the strap thereto, one of the connectionsassociated with each strap including backing members disposedrespectively adjacent opposite faces ofthe end of the strap and anelastomer element interposed between each backing member and theadjacent strap face so that the elements are stressed in shear bymovement of the armature structure to provide relief in a directionlengthwise of the associated strap thereby materially to increase thepermissible deflection thereof.

5. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, fiexures disposed respectively at the opposite ends of thearmature structure, each of the flexures including a deformable strap ofa resilient material having a face whose width is materially greaterthan the strap thickness attached to the armature structure andextending outwardly therefrom with the face of the strap disposed in thedirection of axial movement of the armature structure so that the strapis deflected by the movement thereof, and a connection between theextended end of each strap and the adjacent core structure for attachingthe strap thereto, each of the connections including elastomer elementswhich are stressed in shear by movement of the armature structure toprovide relief in a direction lengthwise of the associated strapsthereby materially increase the permissible deflection thereof.

6. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, a pair of deformable flexure straps of a resilient materialattached respectively at their midpoints to the opposite ends of thearmature structure, and connections between the ends of each strap andthe adjacent core structure for attaching the strap thereto, each straphaving a face whose width is materially greater than the strap thicknesswith the face of the strap disposed in the direction of axial movementof the armature structure so that the strap is deflected by the movementthereof, each connection between the core structure and a respectivestrap including elastomer elements which are stressed in shear bymovement of the armature structure to provide relief in a directionlengthwise of the associated straps thereby materially to increase thepermissible deflection thereof.

7. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, a pair of deformable flexure straps of a resilient materialattached respectively at their midpoints to the opposite ends of thearmature structure, and connections between the ends of each strap andthe adjacent core structure for attaching the strap thereto, each straphaving a face whose width is materially greater than the strap thicknesswith the face of the strap disposed in the direction of axial movementof the armature structure so that the strap is deflected by the movementthereof, each of the connections including elastomer elements abuttingopposite faces of the end of the strap so that the elements are stressedin shear by movement of the armature structure to provide relief in adirection lengthwise of the associated straps thereby materially toincrease the permissible deflection thereof.

8. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, a pair of deformable fiexure straps of a resilient materialattached respectively at their midpoints to the opposite ends of thearmature structure, and connections between the ends of each strap andthe adjacent core structure for attaching the strap thereto, each straphaving a face whose width is materially greater than the strap thicknesswith the face of the strap disposed in the direction of axial movementof the armature structure so that the strap is deflected by the movementthereof, each of the connections including backing members disposedrespectively adjacent opposite faces of the end of the strap and anelastomer element interposed between each backing member and theadjacent strap face so that the elements are stressed in shear bymovement of the armature structure thereby to provide relief in adirection lengthwise of the associated straps thereby materially toincrease the permissible deflection thereof.

9. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direc tion relative to an associated corestructure, a pair of ticxures disposed at the opposite ends of thearmature structure, each of the flexures including a plurality ofdeformable straps of a resilient material extending radially fromequally spaced positions about the armature struc ture, and connectionsbetween the outer end of each strap and the adjacent core structure forattaching the strap thereto, each strap having a face whose width ismaterially greater than the strap thickness with the face of the strapdisposed in the direction of axial movement of the armature structure sothat the strap is deflected by the movement thereof, each connectionbetween the core structure and a respective strap including elastomerelements which are stressed in shear by movement of the armaturestructure to provide relief in a direction lengthwise of the associatedstraps thereby materially to increase the permissible deflectionthereof.

10. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, a pair of flexures disposed at the opposite ends of thearmature structure, each of the flexures including a plurality ofdeformable straps of a resilient material extending radially fromequally spaced positions about the armature structure, and connectionsbetween the outer end of each strap and the adjacent core structure forattaching the strap thereto, each strap having a face whose width ismaterially greater than the strap thickness with the face of the strapdisposed in the direction of axial movement of the armature structure sothat the strap is deflected by the movement thereof, each of theconnections including elastomer elements abutting opposite faces of theend of the strap so that the elements are stressed in shear by movementof the armature structure to provide relief in a direction lengthwise ofthe associated straps thereby materially to increase the permissibledeflection thereof.

11. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an assocated core structure,a pair of flexures disposed at opposite ends of the armature structure,each of the flexures including a plurality of deformable straps of aresilient material extending radially from equally spaced positionsabout the armature structure, and connections between the outer end ofeach strap and the adjacent core structure for attaching the strapthereto, each strap having a face whose width is materially greater thanthe strap thickness with the face of the strap disposed in the directionof axial movement of the armature structure so that the strap isdeflected by the movement thereof, each of the connections includingbacking members disposed respectively adjacent opposite faces of the endof the strap and an elastomer member interposed be tween each backingmember and the adjacent strap faces so that the elements are stressed inshear by movement of the armature structure to provide relief in adirection lengthwise of the associated straps thereby materially toincrease the permissible deflection thereof.

12. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restrainingthestructure in a radial direction relative to an associated corestructure, ilcxurcs disposed respectively at the opposite ends of thearmn ture structure, each of the flexures including a plurality ofdeformable straps of a resilient material attached respectively at theirmidpoints at equally spaced positions about the armature structuresubstantially abutting, the straps being disposed tangentially to thearmature structure with the ends of each strap lying adjacent the endsof adjoining straps, and connections at the adjacent strap ends forattaching the straps to the contiguous core structure, each strap havinga face whose width is materially greater than the strap thickness withthe face of the strap disposed in the direction of axial movement of thearmature structure so that the strap is deflected by the movementthereof, each connection between the core structure and the adjacentstrap ends including elastomer elements which are stressed in shear bymovement of the armature structure to provide relief in a directionlengthwise of the associated straps thereby materially to increase thepermissible deflection thereof.

13. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an associated corestructure, flexurcs disposed rcspectively at the opposite ends of thearmature structure, each of the flexures including a plurality ofdeformable straps of a resilient material attached respectively at theirmidpoints at equally spaced positions about the armature structuresubstantially abutting, the straps being disposed tangentially to thearmature structure with the ends of each straplying adjacent the ends ofadjoining straps, and connections at the adjacent strap ends forattaching the straps to the contiguous core structure, each strap havinga face whose width is materially greater than the strap thickness withthe face of the strap disposed in the direction of axial movement of thearmature structure so that the strap is deflected by the movementthereof, each of the connections including elastomer elements in contactwith the opposite faces of the end of the straps so that the elementsare stressed in shear by movement of the armature structure to providerelief in a direction lengthwise of the associated straps therebymaterially to increase the permissible deflection thereof.

14. For supporting the armature structure of vibration test equipmentwith freedom of movement in an axial direction while restraining thestructure in a radial direction relative to an association corestructure, flexures disposed respectively at the opposite ends of thearmature structure, each of the fiexures including a plurality ofdelormable straps of a resilient material attached respectively at theirmidpoints at equally spaced positions about the armature structuresubstantially abutting, the straps being disposed tangentially to thearmature structure with the end of each strap lying adjacent the ends ofadjoining straps, and connections at the adjacent strap ends forattaching the straps to the contiguous core structure, each strap havinga face whose width is materially greater than the strap thickness withthe face of the strap disposed in the direction of axial movement of thearmature structure so that the strap is deflected by the movementthereof, each of the connections including backing members disposedrespectively adjaccnt opposite faces of the end of the straps and anelastomer elemcnt interposed between each backing element and itscorresponding member so that the elements are stressed in shear bymovement of the armature structure to provide relief in a directionlengthwise of the associated straps thereby materially to increase thepermissible deflection thereof.

Reference-i titcd in the file of this patent UNETED STATES PATENTS2,734,138 Oravec Feb. 7, 1956 FOREIGN PATENTS 33l,82t Great Britain July8, 1930 348,425 Great Britain M May 14, 1931 733,908 Germany Apr. 5,1943

